[Physics-grads-open] PASS talk on Observational Astronomy

[Pooyan Goodarzi]

Hi all,


We will have our next PASS talk on Monday with al talk by Issac. Please 
join us on *November 25th (Monday)* at *noon* (from 12:00 pm to 1:00 pm) 
in the *Nebula Room* (PHYS 3027).


*Issac Ye Lin**, PhD Student
*

Monday, 12:00 pm, Nebula Room (PHYS 3027)

*KBSS-Lyα: Metallicity of Lyman-α Emitters at z~2.5*
*
*
We present a Keck/MOSFIRE composite spectrum for a sample of faint 
KBSS-Lyα emitters (z~2.5) in the Keck Baryonic Structure Survey. With 
the new stacked measurement of [OII] λλ3727,3729Å doublet, we combine 
rest-optical measurements of O, H, and N lines to infer for 12+log(O/H) 
oxygen abundance with photoionization modeling. In our 4-parameter MCMC 
inference (Z_neb, Z_star, N/O, and log(U)), the input emission line 
ratios produce a bimodal metallicity posterior (Z_neb=0.2 Z_sun}, 
Z_neb=0.9Z_sun). Characterized by high O32 ratio (log([OIII]/[OII] = 
0.78), high ionization (log(U) = -2.2), and low dust attenuation (E(B-V) 
= 0.12), we reconcile the lower metallicity peak with other common 
metrics such as z~2-3 MZR,  log(U)-M_sun relation, and electron 
temperature metallicity inference. The elevated O32 hints at 
density-bounded star forming regions in contrast to the more commonly 
assumed ionization-bounded case in photoionization models. Therefore, 
additional parameters are needed to break the degeneracy observed in the 
extreme physical environment of faint LAEs.


If you’re interested in sharing your work as a speaker, please feel free 
to add your name to the spreadsheet [Google Sheet 
<https://docs.google.com/spreadsheets/d/1N3ncf43jdB6aHYHhyWmyHMycxDg4_phHZXLkQvviO0o/edit?usp=sharing>]. 


Best,
Pooyan
Physics and Astronomy Student Seminar (PASS)
*
*
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